Oxidative dehydrogenation catalyst

ABSTRACT

ORGANIC COMPOUNDS ARE DEHYDROGENATED TO COMPOUNDS HAVING A HIGHER DEGREE OF UNSATURATION BY CONTACTING THE FEEDSTOCK IN THE VAPOR PHASE AT AN ELEVATED TEMPERATURE IN THE PRESENCE OF AN OXYGEN-CONTAINING GAS WITH A CALCINED CATALYST CONTAINING A FERROUS GROUP METAL, E.G., NICKEL, IN COMBINATION WITH PHOSPHROUS, AT LEAST ONE GROUP IIA METAL AND OXYGEN. REPRESENTATIVE OF SUCH CONVERSIONS IS THE OXIDATIVE DEHYDROGENATION OF BUTANE TO 1,3-BUTADIENE. THE CONVERSION PRODUCTS ARE VALUABLE COMJPOUNDS PARTICULARYL USEFUL AS INTERMEDIATES FOR THE PREPARATION OF POLYMERIC MATERIALS SUCH AS SYNTHETIC RUBBERS AND THE LIKE.

3,793,225 OXIDATIVE DEHYDROGENATION CATALYST Brent J. Bertus and Darrell W. Walker, Bartlesville, kla., assignors to Phillips Petroleum Company No Drawing. Filed May 6, 1971, Ser. No. 140,973 Int. Cl. B013 11/82 US. Cl. 252-437 6 Claims ABSTRACT OF THE DISCLOSURE Organic compounds are dehydrogenated to compounds having a higher degree of unsaturation by contacting the feedstock in the vapor phase at an elevated temperature in the presence of an oxygen-containing gas with a calcined catalyst containing a ferrous group metal, e.g., nickel, in combination with phosphorus, at least one Group IIa metal and oxygen. Representative of such conversions is the oxidative dehydrogenation of butane to 1,3-butadiene. The conversion products are valuable compounds particularly useful as intermediates for the preparation of polymeric materials such as synthetic rubbers and the like.

The present invention relates to chemical compositions. More particularly, the invention relates to catalyst compositions, their preparation and to catalytic processes employing such compositions, e.g., processes for effecting the dehydrogenation of hydrocarbons.

Thermal catalytic and noncatalytic processes for converting organic compounds to compounds having a higher degree of unsaturation are known. The former are characterized by undesirable side reactions, low order of conversion and yields and poor product selectivity. The catalytic processes are generally characterized by the particular catalytic material employed and the conditions under which the processes are operated, e.g., in the absence or presence of oxygen. While a number of such catalytic processes have attained some measure of commercial success, there is a continuing search to develop catalytic materials for such processes. Preferred as catalysts for such processes are those materials which are more efiicient in minimizing side reactions, in improving conversion rates, in improving yields and selectivities to desired end product, and which have a low susceptibility to deactivation, i.e., are capable of extended periods of operation without regeneration, and can be readily regenerated when necessary. The problem constantly faced by those skilled in the art is the discrement and characterization of the compositions which are highly efficient dehydrogenation catalysts.

A number of catalysts and catalyst systems which include halogens or halogen-releasing compounds have been disclosed. These exhibit many disadvantages in regard to equipment corrosion as well as the expense of continuously feeding, recovering and recycling the relatively expensive halogen materials. Halogen-free catalysts are the most desirable for use in dehydrogenation processes.

The present invention provides a novel catalyst and a novel process for the conversion of organic feedstocks to products having a greater degree of unsaturation and which have the same or lower number of carbon atoms as in the feed. According to this invention, an organic feedstock can be converted to products having a greater degree of unsaturation by contacting said feedstock under dehydrogenation conditions in the vapor phase in the presence of molecular oxygen with a calcined catalytic material comprising phosphorus in association with at least one of the metals nickel, cobalt or iron in combination with at least one Group IIa compound. The invention process is particularly applicable to the conversion United States Patent 0 "Ice of hydrocarbons. Thus, paraffinic hydrocarbons can be converted in good yields to diolefins and/or monoolefins, and monoolefins can be converted to diolefins. The invention is particularly applicable for the production of diolefins from parafiins and particularly useful results are obtained by the dehydrogenation of butane to 1,3-butadiene.

The hydrocarbon feedstocks which are applicable for the oxidative dehydrogenation processes of the present invention comprise dehydrogenatable aliphatic hydrocarbons having from 2 to about 12 carbon atoms per molecule and at least one l l grouping, i.e., at least two adjacent carbon atoms having at least one hydrogen on each carbon. These can be branched or unbranched, cyclic or acyclic, and include paraifins and monoolefins, but paraffins are presently preferred. Particularly preferred as feed materials are dehydrogenatable aliphtic hydrocarbons having from about 4 to about 8 carbon atoms per molecule. The conversion of butane has been found particularly advantageous by the processes of the invention. Some specific examples of other feeds include ethane, propane, isobutane, pentane, cyclopentane, methylbutanes, hexane, Z-methylhexane, octane, 2,4-dimethyloctane, butene-2, 2-methylbutene-1, hexene-Z, octene-l, 3-methylnonene-4, and the like, including mixtures of such compounds.

The novel catalysts of the present invention comprise phosphorus and at least one Group Ha metal in association with at least one metal selected from the group consisting of nickel, cobalt or iron. For convenience, the metal group consisting of nickel, cobalt or iron will be referred to as the ferrous group metals, or simply as the ferrous metals. These elements are not in the elemental state but are combined with sufficient oxygen to form one or more neutral compounds, for example, mixtures of nickel oxide, nickel phosphate, phosphorus oxide, magnesium phosphate, magnesium oxide, iron oxide, cobalt phosphate, and the like.

As noted, the catalysts of this invention comprise a catalytically active association of phosphorus, at least one ferrous metal component, and at least one Group 11a metal component, in combination with suflicient oxygen to satisfy the valence requirements of the several individual components. Thus, the amount of oxygen 'will be percent less the combined percentage of the several individual components, e.g., the sum of phosphorus, ferrous metal and Group IIa components. In forming the catalysts of the invention, nickel is preferred for those embodiments containing a single ferrous metal component; in those embodiments containing a mixture of ferrous metal components, combinations of nickel-cobalt and nickel-iron are preferred.

Generally, the phosphorus component will be present in an amount such as to provide a phosphorus to ferrous metal atomic ratio in the range of 0.01465: 1, preferably 0.1-0.4:1. The Group IIa component will generally be present in an amount suflicient to provide an atomic ratio of Group IIa component to ferrous metal component of at least 0.1:1. Preferentially, the amount of Group IIa component is such as to provide an atomic ratio of Group 11a to ferrous metal in the range of 0.53:1, with an atomic ratio of 1-2:1 being particularly preferred. Of the Group IIa materials, magnesium is presently preferred although beryllium, calcium, strontium, and barium can also be used.

Optionally, the above catalyst components can be associated with a catalytic support material. Presently preferred support materials are selected from the group consisting of silica, alumina, boria, titania, zirconiaor silicaalumina, although other conventional support materials can also be used. The support material, when used, will comprise from about to about 95 weight percent of the total catalyst composite, including support material.

The above-described catalyst compositions can be, op tionally, further associated with a catalyst-modifying quantity of other metals or metal oxides which are effective in improving activity, selectivity, or stability of the catalyst. For example, the catalyst can contain minor amounts of at least one Group Ia material. Additional adjuvants which can be used as modifiers for the catalysts of this invention are chromium, vanadium, molybdenum, ruthenium, rhodium, iridium, platinum, palladium and osmium. These adjuvants, when used, are generally present in minor amounts, for example, in the range of 0.05-10 weight percent, preferably 0.1-5 weight percent, based on the weight of the above-described catalyst compositions.

The catalysts of the present invention can be prepared by any suitable method. Conventional methods such as coprecipitation, impregnation, or dry mixing can be used. In general, any method can be used which will provide a composition containing the above-described elements in the above-described proportions and which will have a catalytic surface area of at least one square meter per gram.

Thus, a phosphorus compound, a ferrous metal compound and a Group Ha compound are combined in any suitable way. Substantially any phosphorus compound, ferrous metal compound and Group IIa metal compound can be employed in the catalyst composition so long as none of the compounds are deleterious to the final dehydrogenation catalyst and so long as essentially all of the elements in the compounds used, other than the phosphorus, ferrous metal, Group Ila compound and oxygen and other than adjuvant elements which contribute to the effectiveness of the catalyst, are removed from the final catalyst by prior washing or by volatilization.

It has been found that, in some instances, minor amounts of still other elements can be tolerated in the catalyst. For example, when magnesium is incorporated into the catalyst by way of the magnesium sulfate compound, minor amounts of residual sulfur can be found in the finished catalyst, and the catalyst can still be effective. On the other hand, halogen residues are generally undesirable in such catalysts. Therefore, when halide compounds are used in the preparation of the catalyst, it is generally advisable to substantially remove the halogen residue such as by sufiicient washing at an appropriate point in the preparation procedure.

Suitable phosphorus compounds include phosphoric acid, phosphorus oxides, ammonium phosphate, alkali metal phosphates, alkaline earth phosphates, and the like, including mixtures thereof.

Similarly, suitable ferrous metal compounds can be used. These can include both organic or inorganic compounds. Some examples of these are nickel oxide, nickel acetylacetonate, nickel nitrate, nickel acetate, nickel sulfate, nickel chloride, and the like, including mixtures thereof. Corresponding compounds of cobalt and iron can also be used.

Similarly, examples of catalyst-modifying materials comprising one or more alkali metal compounds can include lithium nitrate, sodium carbonate, potassium chloride, rubidium acetate, cesium nitrate, sodium phosphate, and the like, including mixture thereof.

Suitable Group IIa metal compounds which can be used in forming the catalyst of this invention inclued magnesium sulfate, magnesium carbonate, calcium carbonate, magnesium bromide, calcium chloride, strontium tartrate, b;.rium hydroxide, and the like, including mixtures there- 0 A convenient method of preparation is to coprecipitate suitable catalyst-forming compounds from aqueous solutions followed by conventional aging, washing, drying, calcining, p e zing, a d the like To these compositions,

either in the wet gel, dry gel or even calcined states, can be mixed or added by impregnation other beneficial metals or even additional amounts of suitable phosphorus or ferrous metal compounds.

When a catalyst support is used, it can conveniently be introduced during the coprecipitation stage of the catalyst preparation. Alternatively, a solid catalyst support, generally in the finished form of a pellet, sphere, or part1 cle, can be impregnated with solutions of the phosphorus compound, a suitable ferrous metal compound and a suitable Group IIa compound. The impregnated solid can then be dried and calcined. When other catalyst-modifying agents are used, they can be introduced into the catalyst either before, during or after the phosphorus, Group 11a and the ferrous metal compounds have been associated with the support.

Whichever catalyst preparation technique is used, the catalyst is activated prior to contact with the feed hydrocarbon by a calcination step. Thus, the finished catalyst is calcined in an oxygen-containing gas such as air at a temperature in the range of from about 900 to about 15 00 F. for a time in the range of about 1 to about 24 hours, or until the catalyst is active for carrying out the oxidative dehydrogenation step.

The hydrocarbon feedstocks can be dehydrogenated according to the processes in the catalyst of the present invention at temperatures in the range of from about 800 to about 1300 F., preferably from about 950 to about 1100 F., at any convenient pressure such as from 7 to about 250 p.s.i.a.; and at a hydrocarbonzoxygen ratio from about 1:05 to about 1:4. The presence of steam is frequently beneficial and a steamzhydrocarbon ratio up to about 50:1 can be used. The hydrocarbon feed rate will generally be in the range of about 50 to about 12-00 GHSV. The fixed catalyst bed is the preferred mode of contact, but other modes, such as a fluidized bed, can also be used.

The dehydrogenation processes of this invention are ordinarily carried out by forming a mixture, preferably preheated, of hydrocarbon feed, the oxygen-containing gas, and the steam (when used) and passing this mixture over the catalyst at the selected temperature. The effluent from the reaction zone is subjected to any suitable separation method to isolate and recover the desired products. Unconverted feeds or partially converted material can be recycled.

Generally, at least trace amounts of oxygenated products are also formed in these reactions. For example, compounds such as furan, ace'taldehyde, furfural and acetic acid can be obtained. In some instances, butadiene can be formed as a by-product of the oxidative dehydrogenation of isopentane to isoprene.

The catalyst can operate for long periods without regeneration. However, if and when regeneration is required, this can be accomplished by simply halting the flow of feed hydrocarbons. Contact with the catalyst to the air and steam can be maintained at the elevated temperature until sufficient activity is restored.

The invention can be illustrated by the following examples.

EXAMPLE I Preparation of catalysts Catalyst A: Sufficient quantities of nickel oxide, magnesium sulfate and phosphoric acid to produce a Ni/Mg/P/O composition having a Ni:Mg:P ratio of 1.0: 0.24:0.13 were blended by dry mixing. The resulting mixture was slurried with water, dried at 300 F. for 3 hours and calcined at 1200" F. for about 16 hours. The calcined mixture was crushed and screened to a 2030 mesh screen size.

Catalyst B: The procedure of Catalyst A was used to produce a Ni/Mg/ P/O catalyst having a nickelzmagnesiumzphosphorus atomic ratio of 1:l:0.l1.

6 Catalysts C, D, E and F: Separate portions of Catalyst While certain embodiments of the invention have been B were contacted with solutions of a sufiicient quantity of described for illustrative purposes, the invention is not cobalt nitrate, ammonium vanadate, chromic acid and limited thereto. Various other modifications or embodiplatinum chloride, respectively, to further promote the ments of the invention will be apparent to those skilled Ni/Mg/P/O catalyst by incorporating 5 percent by weight in the art in view of this disclosure. Such modifications or cobalt, 5 percent by weight vanadium, 1 percent by weight embodiments are Within the spirit and scope of the dischromium, and 0.5 percent by Weight platinum, respecclosure. tively, based on the Ni/Mg/P/O catalyst. The impregnated We claim: catalysts were again calcined at 1000 F. for about 12 1. An oxidative dehydrogenation catalyst consisting eshours. sentially of nickel, phosphorus, magnesium and oxygen EXAMPLE {1 wherein the nickel:magnesiumzphosphorus atomic ratio is 1.0:0.24:0.13. oxldatlve dehydrogenatwn of butane 2. An oxidative dehydrogenation catalyst consisting es- The above-described catalysts were charged to a fixed sentially of nickel, phosphorus, magnesium and oxygen bed reactor and used in several runs in which butane was wherein the nickel:magnesiumzphosphorus atomic ratio is dehydrogenated in the presence of air and steam. Run 111:0.11. conditions with results of these several runs are reported A catalyst according t0 claim 2 wherein there iS in the following Table I. For purposes of comparison, a additionally Present 5 Percent y Weight cobaltcatalyst similar to the invention Ni/Mg/P/O catalyst, A cdllalyst according to Claim 2 wherein there is except that it contained no magnesium, was also tested for additionally Present 5 Percent y Weight vanddlnlnbutane oxidative dehydrogenation. This comparison 5. A catalyst according to claim 2 wherein there is Ni/P/O catalyst is designated as Catalyst G in the table. additionally present 1 percent by weight chromium.

TABLE I.OXIDATIVE DEHYDRO GENATION 0F BUTANE Yields, percent Steam: m

Atomic Adjuvant, hydro- Modiv- Butenes ratio (wt. carbon 04 Air Temp., Time, Conv., ity, Butaan Run Catalyst Ni:Mg:P percent) ratio GHSV GHSV F. hrs. percent percent diene Butane butadiene a To butadienes and butenes. Modivity is a modified selectivity based on analysis of gas phase product for converted hydrocarbons, carbon ozides and unconverted feed.

Norm-As used herein, conversion/yield are reported on same basis as modivity.

The data in the foregoing table show that catalysts 6. A catalyst according to claim 2 wherein there is prepared according to this invention, i.e., catalysts conaddlllonally Present lJbl'dent y Weight Platinumtaining ferrous metal-phosphorus-Group Ila-oxygen com- References Cited ponents and, optionally, activity modifiers such as vanadium, chromium and platinum show substantial activity UNITED STAZTES PATENTS for the oxidative dehydrogenation of butene to form ole- 2926207 2/1960 Folkms et a1 252437 X fins and diolefins. Comparing the similar but magnesium- 2935544 5/1960 Mlner et a1 252437 X free Catalyst G with the invention catalysts, particularly 364956O 3/1972 crime et 260*680 X 0 3,308,188 3/1967 Ba ars 260-680 Catalyst B, shows that the presence of a substantial 3,270,080 8/1966 Christmann amount of magnesium is greatly beneficial in providing high conversion and/or modivity and maintaining such conversion and modivity over a long period of time onstream- 260-680 E, 683.3

PAUL M. COUGHLAN, JR., Primary Examiner US. Cl. X.R. 

